A Review of Technologies for Multistage Wood Biomass Gasification

Currently, small-scale distributed power generation is being intensively developed in Russia and abroad. Given the rise in the rates for the electric and thermal energy, the development of new territories, and the technical infeasible connection to the power supply system, one of the most promising variants of supplying isolated consumers with power is the application of wood biomass gasification technologies. Analysis of the studies in this sphere shows that considerable attention is paid to enhancing the gasification efficiency and ensuring the purity of the gas. These problems are solved using multistage gasification technology. This technology involves the pyrolysis and gasification in separated zones of the gasifier or individual interconnected reactors, which enables achieving the optimal conditions for the conversion of biomass at every separate stage. The major advantage of multistage gasifiers is the production of synthesis gas with a low content of tar. The article represents a review of technologies for multistage wood biomass gasification and comparison of the relevant gasifiers of various types; the basic single-stage and multistage wood biomass gasification technologies are examined and their technical characteristics and examples of their commercial implementation are provided. Analysis of the current situation shows that predominantly foreign multistage wood biomass gasification technologies/plants have found practical application. These technologies allow the produced syngas to be directly used in internal combustion engines and gas turbines without employing expensive auxiliary detarring plants.     

生物质燃料气的燃气热力性质计算方法和程序

生物质能是一种可再生、对环境友好和利用过程中二氧化碳零排放的能源资源, 所以研究生物质气化发电技术意义重大。在烧生物质燃料气的燃气轮机性能计算中, 需要使用生物质燃料气的燃气热力性质数据, 如果将其比热视为常数或采用平均比热都会引起较大误差, 因此需要基于变比热的生物质燃料气的燃气热力性质计算方法。生物质燃料气属于含有不可燃成分的混合气体燃料, 因而将基于变比热的混合气体燃料(含不可燃成分)燃气热力性质的计算方法应用于变比热的生物质燃料气的燃气热力性质计算, 并且用Delphi6 0开发了计算程序。通过对烧某一生物质燃料气的LM2500型燃气轮机的某一工况点热力性能计算, 对该计算方法和程序进行了验证。结果表明, 混合气体燃料(含不可燃成分) 燃气热力性质的计算方法可以应用于生物质燃料气的燃气热力性质计算, 编制的计算程序为烧生物质燃料气的燃气轮机性能计算提供了解决方案。     

生物质热化学转化技术研究进展

文章从生物质的燃烧、气化以及裂解三个方面对近年来国内外学术界在生物质利用方面的进展进行了综述。生物质的燃烧技术中主要介绍了生物质燃烧所利用的锅炉,以及近年来较为热门的生物质与煤的混烧技术。气化方面主要针对近年来学术界较为热门的能量及火用效率的分析进行介绍。在裂解方面,重点介绍了生物质裂解使用的反应器以及在反应器中传热和结焦相关问题。     

Plasma coal reprocessing

Results of many years of investigations of plasma-chemical technologies for pyrolysis, hydrogenation, thermochemical preparation for combustion, gasification, and complex reprocessing of solid fuels and hydrocarbon gas cracking are represented. Application of these technologies for obtaining the desired products (hydrogen, industrial carbon, synthesis gas, valuable components of the mineral mass of coal) corresponds to modern ecological and economical requirements to the power engineering, metallurgy, and chemical industry. Plasma fuel utilization technologies are characterized by the short-term residence of reagents within a reactor and the high degree of the conversion of source substances into the desired products without catalyst application. The thermochemical preparation of the fuel to combustion is realized in a plasma-fuel system presenting a reaction chamber with a plasmatron; and the remaining plasma fuel utilization technologies, in a combined plasma-chemical reactor with a nominal power of 100 kW, whose zone of the heat release from an electric arc is joined with the chemical reaction zone.     

Air-based coal gasification in a two-chamber gas reactor with circulating fluidized bed

During the bed gasification of solid fuels, the process temperature in the reaction zone is not high enough for reaching the maximum rate of the chemical efficiency factor of the gasification process. In order to increase the chemical efficiency factor, it is necessary to supply extra heat to the reaction zone to increase the reaction temperature. In this article, coal gasification in a chamber with forced fluidized bed is considered and it is proposed to supply extra heat with a circulating flow of an inert particulate heat transfer agent. Circulating inert particulate material is successively heated by coal combustion in a cone chamber with bubbling fluidized bed and in a combustion chamber with a spherical nozzle that inhibits the forced fluidized bed. After that, the heat transfer agent heated to 930–950°C enters first in a gasification chamber with bubbling bed and then in a chamber with forced fluidized bed, where it transfers the physical heat to the air fuel mixture. The experiments conducted with crushed Borodinsky coal and inert particulate heat transfer agent (electrocorundum) showed the temperature rise in a gasification chamber with from 760 to 870°C and the increase in the combustible component (CO) concentration in the gasification products by 5.5%. Based on the kinetic equations of the fuel combustion reactions and the CO₂ reduction to CO and on the thermal balance equations of combustion and gasification chambers, the simulation model for the gas composition and the temperature rate calculated by the height of reaction chambers was developed. The experimental temperature rates and product gas compositions are in good agreement with the simulation results based on the proposed kinetic gasification model.     

生物质气化–熔融碳酸盐燃料电池联合循环发电系统性能研究

将生物质气化与熔融碳酸盐燃料电池(molten carbonate fuel cell,MCFC)构建为新型的生物质能高效清洁利用联合循环发电技术,气化产生的富氢气体作为MCFC的燃料,通过燃烧半焦以及MCFC中未利用的燃料为气化反应提供热量,进行生物质气化–MCFC联合循环发电系统的模拟研究。运用Aspen Plus软件搭建系统模型并计算,研究了燃料电池内重整及系统工作压力对系统性能的影响。结果表明：生物质气化–MCFC联合循环发电技术具有较高的系统发电效率,可达50%,比常规生物质气化驱动燃气轮机技术高出10个百分点;对于常压系统无需采用内重整,而对于增压系统,采用内重整对系统性能有较大改善;提高系统工作压力可改善其整体性能,最佳工作压力在0.8~1.2 MPa。     

Development of entrained-flow gasification technologies in the Asia-Pacific region (review)

The gasifier that provides solid fuel conversion to produce syngas with relevant parameters is the key element of plants generating electric and thermal power, producing chemicals from coal. The purpose of this article is to analyze the modern trends in the development of gasification technologies and determine technical solutions providing the high efficiency of gasifiers and the characteristics of generated syngas that meet the requirements established by the process user. Based on the analysis of the world gasification technologies database, which includes all types of gasifiers in use and gasifiers at the construction or design stage, the data on the development of entrained-flow gasification technologies in the Asia-Pacific (AP) countries are discussed. The major constructional components of gasification plants, fuel-feed and syngas cooling methods and their influence on the efficiency and operational reliability are considered. The analysis of technological solutions confirmed the prospectivity of dry-feed entrained-flow technologies. The staged organization of the gasification process makes it possible to solve issues of increasing the economic and environmental indicators of gasification plant operation. The basic directions of modernization of entrained-flow gasifiers for improving their technical-and-economic perfomance was determined.     

空气气氛下褐煤和木屑共气化特性模拟

针对煤和生物质在单独气化过程中存在的转换率低、气体热值低和焦油含量高等问题,笔者通过CHEMKIN软件建立流化床反应模型对木屑和褐煤的空气气化进行模拟试验,研究生物质掺混比例（木屑/褐煤）、空气当量比,对产气组分、气体产率、碳转化率、热值和气化效率的影响.分析结果表明,通过建立柱塞流反应模型,依据燃料自身特性,选取合适的掺混比和空气当量比（ER值）,可以得到高热值气体,并提高气化效率.     

秸秆类生物质加压气化特性研究

采用热重分析与气相色谱分析(TG-GC)相结合的方法,开展了水蒸气气氛下生物质(麦秸)加压气化特性研究,探讨压力对反应动力学特性与气化产物的影响。实验结果表明生物质常压气化与加压气化特性有显著差异;加压条件下,麦秸的气化反应过程受化学反应动力学和扩散作用控制。麦秸水蒸气气氛下的热解阶段可视为一级反应,半焦气化阶段视为缩核反应;加压下热解、气化的表观活化能和频率因子均随反应压力的提高而增加。水蒸气对生物质热解气化具有活化作用,相比N2气下麦秸的表观活化能降低。此外,生物质水蒸气气化产物中H2浓度最大,达到50%以上,表明水蒸气是生物质气化制氢适宜的气化介质;随着气化压力的提高,CO2和CH4浓度增加,而CO浓度降低。     

热化学过程中生物电能的产生

目前，生物能被视为在未来有潜力提供大部分可再生 能源的储备，它可以以气体、液体或固体燃料形式提供生物 燃料或者用于发电和供热。有三种主要的提供生物能的途 径，即热转换、生物转换和物理转换，这些方法都需要配置 和设计各种各样的化学反应器。文章重点研究能高效、低成 本、高度通用地提供大量能量、燃料和化学产品的热化学转 换过程。特别研究和讨论了所谓的先进的气化和快速热解技 术，其主要产品可以是气体、液体或固体燃料，而其副产品 则是电能和/或热能、液体燃料及大量的化学品。文章还对 阻碍不同技术的市场配置的主要技术性和非技术性壁垒进 行了概述。     

Modern State and Topical Issues of Studying Solid Fuel Particle Primary Fragmentation Processes as Applied to Biomass Combustion and Gasification in Fluidized and Dense Bed (Review)

It is shown that it is important to take into account the variation of particle sizes due to their fragmentation in fluidized bed biomass combustion. The present state of investigations into the fragmentation process is analyzed. It is shown that primary fragmentation, a process involving cracking and disintegration of initial fuel particles into two or more parts due to thermal stresses and growth of pressure in the particles during their rapid heating at the drying and devolatization stages is the most essential issue. Factors causing the cracking of fuel particles and the nature of this process are considered. The particle fragmentation quantitative characteristics and criteria are analyzed. It is shown that the particle critical diameter is the simplest criterion for estimating the susceptibility of different fuels to fragmentation. The main factors influencing the occurrence of primary fragmentation, namely, particle size, heating rate, bed temperature, and fuel characteristics, are considered. The list of fuel’s main characteristics affecting its primary fragmentation includes the volatiles content, porosity, moisture and ash content, susceptibility of particles to swelling or shrinking, and the organic part composition. Matters concerned with predicting primary fragmentation of fuels are considered. Information about the interrelation between the main characteristics of fuels, their susceptibility to primary fragmentation, and its nature is presented. In view of biomass properties and its combustion conditions, both of the primary fragmentation mechanisms, namely due to devolatization induced stresses and thermal stresses, are supposed to take place. It can be expected that the domination of one or another mechanism will depend on the combination of particle size and heating temperature. The lines of and methods for studying the nature of biomass particles primary fragmentation and its quantitative characteristics under different conditions are outlined. The data obtained as a result of such fundamental investigations will form the basis for elaborating methods for designing furnace devices and gasifiers operating on biomass taking into account the effect of particle fragmentation on the combustion, gasification, carryover, and heating surface contamination processes.     

生物质气化机理及应用

介绍了生物质气化机理、工艺及设备,并介绍了目前应用较多的生物质气化供气和生物质气化发电方式,指出了生物质气化技术目前面临的问题,提高效率和可靠性、降低飞灰和焦油含量等是今后生物质气化技术应用的主要研究课题。     

两种不同再生方式下含碳能源直接制氢的比较

为了确定CO2吸收剂的不同再生方式对整个制氢过程的影响,根据含碳能源直接制氢的基本思路,构建了2种不同的制氢系统:碳部分转化(PCC)再生供热和化学链(氧化镍NO)反应供热。利用ASPENPlus软件,对2种不同再生方式下制氢系统的能量平衡和热平衡进行了热力学计算,分析系统的冷煤气效率,并对2种不同的再生方式对制氢过程中气体产物和固体产物组成的影响进行了初步分析。结果表明,相同的进料条件下,PCC过程中约68%的碳在气化炉中被气化时,系统可实现热平衡,此时冷煤气效率达0.74,而NO过程中只有51%的碳用于气化生成氢气,系统冷煤气效率只有0.67。即在该文的分析条件下,PCC过程更适合于为含碳能源直接制氢系统中的吸收剂再生供热。     

流化床常压空气部分气化和半焦燃烧的试验研究

为进行煤的多联产方案研究,在1 MW循环流化床热电气多联产试验装置上,选取兖州煤、大同煤为试验煤种进行了部分空气气化和半焦燃烧试验。试验结果表明,空气部分气化方案得到的煤气热值较低,为3~5 MJ/m3,在气化炉中的碳转化率为40%~70%,剩余半焦被送入循环流化床反应器中燃烧,该系统的总体转化效率为90%左右。气化炉床层温度对气化炉碳转化率影响较大,随着温度升高其碳转化率明显提高,而燃烧炉燃烧效率呈下降趋势。石灰石的加入除了对焦油的裂解有一定的促进作用外,还具有脱除硫化氢作用,当[Ca]/[S]为3时,脱硫效率为90%。气化炉的给煤量、燃烧炉运行温度随气化炉鼓风温度提高而增加。     

采用再燃技术的电站锅炉炉膛热力计算方法研究

在燃煤粉电站锅炉各种低NOx燃烧技术中,燃料分级燃烧(再燃)技术是降低NOx排放的有效方法之一。根据采用再燃技术的炉膛燃烧与放热特点,对已有的炉膛分区段热力计算方法进行了改进,将主燃烧区和再燃区作为两个主要放热区段,推导了采用再燃方式的炉膛热力计算方程式,并给出了某200 MW燃煤粉锅炉炉膛的校核热力计算示例。     

Optimization of biomass fuelled systems for distributed power generation using Particle Swarm Optimization

With sufficient territory and abundant biomass resources Spain appears to have suitable conditions to develop biomass utilization technologies. As an important decentralized power technology, biomass gasification and power generation has a potential market in making use of biomass wastes. This paper addresses biomass fuelled generation of electricity in the specific aspect of finding the best location and the supply area of the electric generation plant for three alternative technologies (gas motor, gas turbine and fuel cell-microturbine hybrid power cycle), taking into account the variables involved in the problem, such as the local distribution of biomass resources, transportation costs, distance to existing electric lines, etc. For each technology, not only optimal location and supply area of the biomass plant, but also net present value and generated electric power are determined by an own binary variant of Particle Swarm Optimization (PSO). According to the values derived from the optimization algorithm, the most profitable technology can be chosen. Computer simulations show the good performance of the proposed binary PSO algorithm to optimize biomass fuelled systems for distributed power generation.     

木块在流化床气化炉内气化特性的试验研究

利用自行设计的小型流化床试验装置系统,对城市生活垃圾中木块组分在不同的反应温度、不同的过量空气系数下进行了空气气化实验。分析了在流化床气化炉中,这些反应条件对木块转化为气化气的影响以及在不同的气化反应条件下,木块气化气成分、产气率、气化气热值及气化效率的变化规律。最后,提出了流化床城市生活垃圾气化熔融技术中一些有价值的运行参数范围。     

IGCC燃用低热值燃料的燃气轮机运行性能优化

天津IGCC是中国第一座整体煤气化联合循环电站。系统中燃气轮机的燃料为气化炉产生的热值较低的合成气,作为国内第一台应用于IGCC技术的燃气轮机,在运行过程中存在着合成气热值与设计值偏差大、烧嘴过热、燃烧室偏烧等问题。针对存在的问题,首先介绍了IGCC电站燃用低热值燃料的燃气轮机与普通燃气轮机在燃料、燃烧方式、燃烧器结构等方面的区别;然后结合实际运行参数分析,重点对存在的问题提出性能优化方案及措施。对燃用低热值燃料的燃气轮机后续发展具有一定的借鉴意义。     

Calculation of the fixed bed coal gasification regimes by the use of thermodynamic model with macrokinetic constraints

We discuss an equilibrium model of a fixed-bed solid fuel gasification process that takes into account macrokinetic constraints imposed on the rates of heterophase processes and allows the pyrolysis and gasification processes to be described in a fairly simple manner with the use of thermal analysis data. The results of calculations are compared with the measured parameters characterizing the Azeisk coal steam-air gasification process that were obtained in experiments on a laboratory setup.     

Complex analysis of energy production technologies from solid biomass in the Ukraine

The results of the energetic, economic, and environmental analyses of technologies of energy production from solid biomass are considered. Examples of the introduction of the technology of the direct combustion of biomass (straw and wood) in a boiler installation, a domestic boiler, and a combined heat and power plant (CHPP) are considered. The results indicate the energetic and environmental reasonability of implementation of such projects. From the economic viewpoint, the introduction of the boilers that use the biomass is profitable with the substitution of natural gas for the state-financed and industrial consumers, and the CHPP operation with the use of biomass is profitable with selling the electrical energy by the “feed-in” tariff.